[vtk-developers] Upcoming features, careful with CVS updates...

[Will Schroeder]

*Summary*:
There are upcoming changes to VTK timers (which may affect interactor 
styles); and the addition of timer-based widgets (e.g., 
vtkBalloonWidget). Please delay CVS updates for a day or two while we 
stabilize.

*Details:
*Dave Cole and I have been working on the timer methods found in 
vtkRenderWindowInteractor. Originally, these methods implicitly assumed 
that only one timer at a time was created, and they were only used by 
subclasses of vtkInteractorStyle. However, we are beginning to add 
widgets (like vtkHoverWidget and vtkBalloonWidget) that depend on 
timers. (These widgets perform an action if the mouse pointer does not 
move for a certain time and the pointer is over top of a vtkProp. For 
example, a text string or caption associated with the vtkProp can be 
popped up. Eventually we will have widgets that popup thumbnails and/or 
hyperlinks.)

Such widgets require that multiple timers run simultaneously, meaning 
that timers must be distinguished by a timer id. Also, the InvokeEvent() 
method must provide the timer id associated with the event (e.g., 
vtkCommand::TimerEvent,(void*)&timerId);) so that observers know whether 
an event is for them or not.

While the code is fairly straightforward, it is a bit tricky to 
simultaneously develop and thoroughly test the code on multiple 
platforms (Win32, X, Carbon, Cocoa). We plan on checking the code in 
stages starting early Tuesday or Wednesday (I will warn everybody). 
Unfortunately  there may be some instability while we coordinate our 
efforts which we will do our best to avoid.  I will give the all clear 
once we believe everything is stable.

Note that backward compatibility should be preserved: the old 
CreateTimer(timerType)/DestroyTimer(void) methods are being augmented by 
new methods that deal with timer ids 
(timerId=CreateOneShotTimer(duration); 
timerId=CreateRepeatingTimer(duration); ResetTimer(timerId) and 
DestroyTimer(timerId)).

Please let me know if you have concerns, suggestions, etc.

Will